The present invention relates to a rubber composition and a tire using the rubber composition.
In recent years, grip performance and rolling resistance property are required to be improved in a tread as properties necessary for a tire. Both grip performance and rolling resistance property relate to hysteresis loss of a rubber. Generally, if hysteresis loss is large, grip force is large and braking performance is improved, thus, grip performance is excellent, but deterioration of rolling resistance property is caused since rolling resistance becomes large. As described above, since grip performance and rolling resistance property are in an antithetic relation, various rubber compositions for a tire have been proposed so as to satisfy both properties at the same time.
In order to improve both grip performance and rolling resistance property together, a rubber composition compounded with silica as a reinforcing agent, in which grip performance and rolling resistance property are improved in favorable balance, is known. However, the rubber composition has a problem that improvement effects of both grip performance and rolling resistance property are not sufficient.
As a process of further lowering rolling resistance, a method of compounding silica and a silane coupling agent is also known. Rolling resistance can be lowered by chemically bonding a rubber and silica with a silane coupling agent due to compounding the silane coupling agent. However, when the silica and silane coupling agent are kneaded, it is necessary to sufficiently react at a high temperature, and a functional group in the silane coupling agent reacting with a rubber initiates a reaction during processing such as kneading, which causes a problem that a phenomenon of rubber scorch called gelation occurs.
JP-A-2001-172434 discloses a rubber composition for a tread showing excellent wet grip performance under a high temperature and comprising specified amounts of a rubber component containing a specified amount of a specific solution-polymerized styrene-butadiene rubber, a silica and a specific aromatic oil, however, rolling resistance is not lowered in the rubber composition for a tread.